Health risk assessment of Emamectin Benzoate insecticides exposure in farmer: a case study of agricultural area, Nikompattana Sub-district, Bang-Rakam District, Phitsanulok, Thailand

Thailand is an agricultural country where rice and corn are major production crops, and Emamectin benzoate (EB1) is widely applied for insect control. This study aimed to assess the potential health risks of EB1 exposure among farmers in Nikompattana Sub-District, Bang-Rakam District, Phitsanulok Province, using dermal exposure assessment through patch sampling, biological monitoring of blood samples, and EB1 residue analysis in agricultural products (rice and corn) and environmental matrices (soil and water). Hazard Quotients (HQ) were calculated for dermal and ingestion exposure pathways, and the cumulative Hazard Index (HI) was determined to evaluate overall non-carcinogenic risk. Patch sampling showed detectable EB1 residues on clothing surfaces, while samples placed under clothing did not detect EB1, indicating reduced dermal absorption with protective clothing use. Blood analysis using LC–MS/MS detected total EB1 and its metabolites in 10 farmers (14.3%) during the rice season and 42 farmers (60.0%) during the corn season. Total EB1 concentration was calculated from the combined quantification of EB1a, EB1b, A-EB1a, and A-EB1b, with mean post-application concentrations of 0.16 ng/mL in the rice season and 1.15 ng/mL in the corn season. Although detectable, these concentrations remained below reference systemic toxicity thresholds, and the single time-point sampling design may underestimate peak internal exposure. EB1 residues were detected in 31.4% of rice samples and 15.7% of corn samples, with several exceeding acceptable ingestion HQ thresholds. Soil monitoring revealed EB1 contamination in 97.1% of samples, while all surface water samples remained below detection limits. Cumulative HI analysis showed that 47.1% of farmers had HI values greater than 1, with higher proportions among female farmers, those with abnormal BMI, and farmers with underlying diseases, indicating increased susceptibility to combined exposure. Mixed pesticide application was strongly associated with elevated HI outcomes. The exclusion of air sampling represents a limitation, as inhalation could not be quantified despite its relevance during spraying. These findings highlight occupational and environmental exposure concerns, supporting the need for regulatory monitoring, establishment of Maximum Residue Limits (MRLs), strengthened pesticide-use guidelines, and enhanced protective measures to safeguard farmer and consumer health.